In the nuclear field, there are a number of installations comprising shielded enclosures or cells inside which work operations are carried out making it possible to qualify this type of "high activity" cells. Work operations are carried out inside this type of cell, namely the dismantling of certain irradiated units, the processing of certain irradiated fuels and all operations unable to be carried out by human operators owing to the lack of bilogical and radiological protection. These cells have several orifices with at least one orifice being used for control, visualizing and the follow-up of the operations carried out inside the cells. Most of the time, these orifices include one internal pane intended to ensure the protection of outside operators against alpha radiations, and a shielding window intended to provide the biological protection of operators outside the cell.
As shown on the FIGURE, the orifice concerned has been shown as a section by the draftsman so as to see clearly in the wall 1 of the enclosure of the cell the internal pane 2 placed towards the inside 3 of the cell, and a shielding window 5 placed on the outer side 4 of the wall 1, but much thicker than the pane. The latter is transparent, with a thickness of between 30 to 40 millimeters and is made of lead glass. The shielding window 5 has a particular "staircase" type shape enabling it to ensure highly effective biological protection against the various radiations. Its thickness is preferably complementary to that of the pane 2 so as to occupy the entire thickness of the wall 1 of the cell.
During a certain number of months of use of the cell, it is frequent that vision through the orifice is altered by a soiling of the face of the pane 2 located against the shielding window 5. It may be that in particular humidity occurs between these two elements and that observation through the orifice is either altered or no longer satisfactory. It is then vital to clean this outer face of the pane 2 located against the shielding window 5.
Several methods have been used to clean this protection pane 2.
One first solution consists of emptying the inside of the cell of the irradiating equipment it contained, but this operation is not always reliable for reasons of storage and creates operating restraints.
One second operation consists of constructing inside 3 the cell in front of the pane 2 a lead protection biological wall. On the other hand, this material is then contaminated, which of necessity poses a problem of decontaminating this element, thus creating other operation restraints.